Lara finds what looks like a Smith and Wesson revolver in Siberia early in the game. Not sure what kind, have to go back and grab a screenshot.

She's still using the Remington R1 Enhanced from the first game as the "Semi-auto pistol", in a cutscene in England, Syria (with infinite spare ammo), and Siberia. Comes in normal and DLC-only "Accipitor Noxa" version in matte black